The present invention relates to improvement of the quality of existing ultrasound diagnostic examination by combining a B-scan visualization technique with a Two-Frequency Attenuation Method technique to obtain high quality ultrasound diagnostic examination including non-invasive determination the type of the issue matter under ultrasound investigation.
For many years specialists in ultrasound diagnostic field trying to develop an ultrasound diagnostic method and apparatus which can provide information to differentiate type of tissue through measuring attenuation data in a living body or by finding a pattern of the tissue images. There are many attempts to reach that goal by using spectrum analyzes of reflected signals like U.S. Pat. No. 6,007,489 to Yost et al., European Patent No. 11840135 to Hironaka and many others that could not come up with an objective and reliable method for clinical applications. Some specialists like European Patent No. PCT/IB2014/067105 to Schneider, European Pat. No. PCT/CA2014/2014/050480 to Sadeghi, U.S. patent Ser. No. 14/096,960 to Anuja, European Pat. No. PCT/US2014/011631 to Chen and others tried to find a pattern in a tissue images to differentiate the type of tissue. All attempts to find some positive information to improve B-scan visualization examination to differentiate type of tissue was not successful since reflected echo-signals depend not only on attenuation information from inside of the tissue structure but also on the angle of incident of the ultrasound pulses to reflected surface, its geometry and roughness. Attempts to find a system employing ultrasound methods for determination the nature of tissue within a living body is still continuing. One such system is disclosed in U.S. Pat. No. 5,361,767 to Yukov. This system determines a type of tissue by using methods and apparatuses for a “Two-Frequency Method” of tissue characterization which is based on applying two different frequencies and by registering reflected signals to calculate a differential attenuation coefficient of the tissue through formula:a(f2)−a(f1)=[A1(f2)/A2(f2)−A1(f1)/A2(f1)]/2 l dB/Cm/MHz,where a(f1) and a(f2)—attenuation coefficient on frequencies f1 and f2 accordingly; A1 (f1), A2(f1) and A1(f2), A2(f2) are amplitudes of the reflected signals from front and rare boundaries of a layer on frequencies f1 and f2 accordingly; l—is a thickness of a layer.
Author describes requirements for the reflected signals to be processed through mathematical algorithm since as mentioned there is no direct dependency between reflected signals and attenuation information. For that purpose, author suggests obtaining objective information related to attenuation data through analyses of the shape, width and registered time of reflected signals on applied two different frequencies. Chinese Patent No. CN1113631C to Korotkoff discloses a two-frequency method and apparatus which is based on a developed “Two-Frequency Method” described in U.S. Pat. No. 5,361,767. Author suggests subtraction of reflected signals automatically on two different frequencies and displaying the results as a two-dimensional attenuation image on the screen. As mentioned since there is no direct dependency between reflected signals and attenuation information the apparatus in Chinese Pat. No. CN1113631C for automatic two-dimensional attenuation image display cannot obtain objective attenuation information and it will. be impossible to apply in the clinical environment as an objective diagnostic method.
U.S. Pat. No. 5,361,767 to Yukov suggests using the Two-Frequency Method as a Tissue Characterization Method together with a B-scan tissue structure image information, which makes it easier to find a spot of interest for measurement of attenuation. This reference also suggests using the same B-scan transducer simultaneously, in sequence or alternately as a B-scan image visualization method and as a transducer for a Two-Frequency Attenuation Method in order to calculate attenuation data from a spot of interest for generating tissue characterization information. Yukov did not mention that there are fundamental differences between the requirements for B-scan transducers and Two-Frequency Attenuation Method transducers. B-scan transducers require different types of excitation pulses which must be very sharp and short to achieve high resolution of tissue structure image. In contrast, the excitation pulse for a Two-Frequency Method transducer consist of several sine-waves.
Another big difference is that a B-scan transducer requires multiple piezo-elements but a Two-Frequency Method transducer requires only one piezo-element (i.e., only one emitter-receiver source). Because of these differences there are limitations for applying a regular B-scan transducer for both methods. Very sharp and short excitation pulses of a B-scan imaging system produces a very high resolution of the tissue structure images. However, in many cases there is still not enough information to differentiate the type of abnormalities in the patient's body. B-scan imaging systems need some extra information to resolve this problem. One type of needed information would account for different attenuation values according to the type of tissue.
Applying B-scan image visualization combined with a Two-Frequency Attenuation Method for tissue characterization can improve quality of the ultrasound diagnostic examinations and will make it possible to determine types of the tissue non-invasively in a living entity.